HDFN & AIHA EXAM 2024-2025
What kind of hemoglobin does a fetus have? How much, approximately does the
newborn carry?
Hgb F. Hgb F at birth is primary hemoglobin (60-80%)
What is distinctive about Hgb F?
high affinity for oxygen, which holds onto the oxygen tighter than HgbA. This allows easy
transport of oxygen from maternal circulation to fetal RBC during the entire pregnancy.
What are Hgb levels in a Preterm Newborn, Normal Newborn?
Pre-Term Newborn: ~12-14 g/dL
Normal Newborn: ~16-18 g/dL
When does a newborns Hgb begin to trend and where abouts does it land?
At 4-8 weeks it goes to ~9-11gL
Why does Hbg fall after birth?
Hgb F has a higher affinity than Hgb A, for O2. Once the baby is born there is plenty of
O2 available to the baby, it is not competing to drawn O2 from the maternal system, so it
doesn't need a high affinity Hgb.
The Hgb A releases the O2 easier to the tissues.
Erythropoietin (EPO) and RBC production declines.
Iatrogenic blood loss?
Blood loss resulting from testing samples being drawn.
What causes HDFN?
, -Baby inherits antigen from father that mother lacks.
-Small amounts of fetal blood enters mother's circulation.
-Mother forms an IgG antibody.
-IgG antibody crossed the placenta and attacks baby's red cells.
pository Presentation
What are three different types of HDFN. Say how common and how severe?
• Rh (due to anti-D): most severe HDFN. Relatively uncommon occurrence.
• Other: Anti-C,-c,-E,-e,-K,-k,-Fya,-Jka,etc • Usually not as severe as HDFN due to anti-D,
EXCEPTION: anti-K can cause severe HDFN. Occurs rarely
ABBO: most common. least severe HDFN
Why is HDFN due to anti-K such a big deal?
Due to the fact that the anti-K can attack red cell precursors in the fetus/neonate,
causing a very severe Anemia. The anti-K titers are almost as informative as the D titers
in that they can be low and yes the baby can be severely affected.
Which IgGs are good at crossing the placenta?
IgG1 and IgG3 more efficient at causing hemolysis.
What are the factors affecting maternal immunization?
• Immunogenicity of the paternal antigen.
• Number of antigen sites on fetal cells; is antigen developed at birth/on cord cells?
• Route and number of exposures to antigen. ie. Transfusion, prior pregnancies
• Mother's immune competence; can the mother make antibodies?
• Placental passage of antibody; IgG1 and IgG3 are really efficient at crossing the
placenta where as IgG2 is least efficient at crossing placenta. Wouldn't really expect to
see an IgG2 or an IgG4 causing a problem.
• Protection of the fetus by maternal ABO antibodies.
What kind of hemoglobin does a fetus have? How much, approximately does the
newborn carry?
Hgb F. Hgb F at birth is primary hemoglobin (60-80%)
What is distinctive about Hgb F?
high affinity for oxygen, which holds onto the oxygen tighter than HgbA. This allows easy
transport of oxygen from maternal circulation to fetal RBC during the entire pregnancy.
What are Hgb levels in a Preterm Newborn, Normal Newborn?
Pre-Term Newborn: ~12-14 g/dL
Normal Newborn: ~16-18 g/dL
When does a newborns Hgb begin to trend and where abouts does it land?
At 4-8 weeks it goes to ~9-11gL
Why does Hbg fall after birth?
Hgb F has a higher affinity than Hgb A, for O2. Once the baby is born there is plenty of
O2 available to the baby, it is not competing to drawn O2 from the maternal system, so it
doesn't need a high affinity Hgb.
The Hgb A releases the O2 easier to the tissues.
Erythropoietin (EPO) and RBC production declines.
Iatrogenic blood loss?
Blood loss resulting from testing samples being drawn.
What causes HDFN?
, -Baby inherits antigen from father that mother lacks.
-Small amounts of fetal blood enters mother's circulation.
-Mother forms an IgG antibody.
-IgG antibody crossed the placenta and attacks baby's red cells.
pository Presentation
What are three different types of HDFN. Say how common and how severe?
• Rh (due to anti-D): most severe HDFN. Relatively uncommon occurrence.
• Other: Anti-C,-c,-E,-e,-K,-k,-Fya,-Jka,etc • Usually not as severe as HDFN due to anti-D,
EXCEPTION: anti-K can cause severe HDFN. Occurs rarely
ABBO: most common. least severe HDFN
Why is HDFN due to anti-K such a big deal?
Due to the fact that the anti-K can attack red cell precursors in the fetus/neonate,
causing a very severe Anemia. The anti-K titers are almost as informative as the D titers
in that they can be low and yes the baby can be severely affected.
Which IgGs are good at crossing the placenta?
IgG1 and IgG3 more efficient at causing hemolysis.
What are the factors affecting maternal immunization?
• Immunogenicity of the paternal antigen.
• Number of antigen sites on fetal cells; is antigen developed at birth/on cord cells?
• Route and number of exposures to antigen. ie. Transfusion, prior pregnancies
• Mother's immune competence; can the mother make antibodies?
• Placental passage of antibody; IgG1 and IgG3 are really efficient at crossing the
placenta where as IgG2 is least efficient at crossing placenta. Wouldn't really expect to
see an IgG2 or an IgG4 causing a problem.
• Protection of the fetus by maternal ABO antibodies.
